(1) Field of the Invention
This invention relates to improvements in ossicular replacement prosthetises.
(2) Prior Art
In the middle ear a chain of three small bones called the hammer (malleus), the anvil (incus) and the stirrup (stapes) in the tympanic cavity, transmit the sound (in the form of vibrations) from the eardrum to the oval window (fenestra ovalis) in the membrane separating the middle ear from the inner ear.
This chain can become broken (e.g. due to injury) or be incomplete (e.g. due to a congenital defect) and so the hearing of the person may be wholly or partially impaired.
To overcome this problem, surgeons have implanted partial ossicular replacement prostheses (P.O.R.P.) or total ossicular replacement prostheses (T.O.R.P.) in the middle ear, dependent on whether or not the stapes (stirrup) is intact, to permit sound to travel from the eardrum to the inner ear.
While such prostheses have provided a partial solution to the problem, they generally have flat tops or caps which bear against the tympanic membrane of the eardrum. If the prostheses becomes tilted or partially dislodged, the edge of the top or cap creates a pressure point on the membrane and may result in permanent damage to the membrane.